Caption: Fused bones in arthritic wrist. X-ray of a section through the left wrist of a 43-year-old patient affected by severe rheumatoid arthritis. Rheumatoid arthritis is a degenerative autoimmune disease that mainly affects the capsule (synovium) around the synovial (flexible) joints, causing chronic inflammation. It can be a debilitating and painful condition, which can lead to loss of functioning and mobility. Here, it has caused synostosis (fusion) of the carpal (wrist) bones.